Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems. Body mass index (BMI), a measurement which compares weight and height, defines people as overweight (pre-obese or overweight) if their BMI is between 25 and 30 kg/m2, and obese when it is greater than 30 kg/m2. Obesity is a leading preventable cause of death worldwide, with increasing prevalence in adults and children, and authorities view it as one of the most serious public health problems of the 21st century.
Obesity increases the risk of many physical and mental disorders. Excessive body weight is associated with various diseases, particularly cardiovascular diseases, diabetes mellitus type 2, obstructive sleep apnea, certain types of cancer, and osteoarthritis. These diseases are either directly caused by obesity or indirectly related through mechanisms sharing a common cause such as a poor diet and/or a sedentary lifestyle. One of the strongest links is with type 2 diabetes. Excess body fat underlies 64% of cases of diabetes in men and 77% of cases in women. Increases in body fat alter the body's response to insulin, potentially leading to insulin resistance.
Obesity is most commonly caused by a combination of excessive energy intake, lack of physical activity, and genetic susceptibility, although a few cases are caused primarily by genes, endocrine disorders, medications or psychiatric illness. Since the discovery of leptin in 1994, many other hormonal mechanisms have been elucidated that participate in the regulation of appetite and food intake, storage patterns of adipose tissue, and development of insulin resistance, including ghrelin, insulin, orexin, PYY 3-36, cholecystokinin, and adiponectin.
Adipokines are mediators produced by adipose tissue; their action is thought to modify many obesity-related diseases. Leptin and ghrelin are considered to be complementary in their influence on appetite, with ghrelin produced by the stomach modulating short-term appetitive control (i.e., to eat when the stomach is empty and to stop when the stomach is stretched). Leptin is produced by adipose tissue to signal fat storage reserves in the body, and mediates long-term appetitive controls (i.e., to eat more when fat storages are low and less when fat storages are high). Although administration of leptin may be effective in a small subset of obese individuals who are leptin deficient, most obese individuals are thought to be leptin resistant and have been found to have high levels of leptin. This resistance is thought to explain in part why administration of leptin has not been shown to be effective in suppressing appetite in most obese people.
While leptin and ghrelin are produced peripherally, they control appetite through their actions on the central nervous system. In particular, leptin and ghrelin and other appetite-related hormones act on the hypothalamus, a region of the brain central to the regulation of food intake and energy expenditure. There are several circuits within the hypothalamus that contribute to its role in integrating appetite, with the melanocortin pathway being the most-well understood. The circuit begins with the arcuate nucleus, an area of the hypothalamus that has outputs to the lateral hypothalamus and ventromedial hypothalamus, the brain's feeding and satiety centers, respectively.
The arcuate nucleus contains two distinct groups of neurons. The first group co-expresses neuropeptide Y (NPY) and agouti-related peptide (AgRP) and has stimulatory inputs to the LH and inhibitory inputs to the VMH. The second group co-expresses pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) and has stimulatory inputs to the VMH and inhibitory inputs to the LH. Consequently, NPY/AgRP neurons stimulate feeding and inhibit satiety, while POMC/CART neurons stimulate satiety and inhibit feeding. Both groups of arcuate nucleus neurons are regulated in part by leptin. Leptin inhibits the NPY/AgRP group while stimulating the POMC/CART group. Thus a deficiency in leptin signaling, either via leptin deficiency or leptin resistance, leads to overfeeding. This may account for some genetic and acquired forms of obesity.
Dieting and physical exercise are the mainstays of treatment for obesity. To supplement these activities, or in case of failure, anti-obesity drugs may be taken to reduce appetite or inhibit fat absorption. In severe cases, surgery is performed or an intragastric balloon is placed to reduce stomach volume and/or bowel length, leading to earlier satiation and reduced ability to absorb nutrients from food. Maintaining this weight loss is frequently difficult and often requires making exercise and a lower food energy diet a permanent part of a person's lifestyle. Success rates of long-term weight loss maintenance with lifestyle changes are low, ranging from 2-20%.
A limited number of medications are available for the treatment of obesity. Concerns about side effects have diminished enthusiasm for appetite-suppressant drugs, particularly fenfluramine, sibutramine, and phentermine, which carry serious risks and have been withdrawn from the market. Phentermine is approved only for short-term use. Orlistat (Xenical) is a medication that blocks the absorption of dietary fat and is also approved for longer-term use. However, it causes unpleasant side effects (greasy stool), and requires supplementation with fat-soluble vitamins.
Although surgery (such as gastric bypass) is the last resort for the treatment of obesity, it can be extremely effective. However, it should be performed at an experienced surgical center, because such operations can carry significant risks, especially in the post-operative period. Consensus recommendations are to limit surgical therapies to patients with morbid obesity (BMI >40, BMI >35 plus co-morbidities, or BMI >30 with uncontrollable diabetes).
A number of weight-loss pills are available at local drugstores, supermarkets or health food stores. Even more options are available online. Most have not been proved effective, and some may be dangerous. Table 1 (below) shows common weight-loss pills and what the research shows about their effectiveness and safety.
Herbal extracts are often impure and contain so many different substances, that it is difficult to assess if the mixture as a whole is efficacious, much less what constitutes an effective dosage. With hundreds or more different compounds in the mixture, it could be more than one compound required for activity, or one compound inhibiting activity of another compound, so the source and processing of the original source material may result in an inactive or even dangerous product.
TABLE 1Anecdotal Products for Weight Loss. Sources:U.S. Food and Drug Administration, 2010; NaturalMedicines Comprehensive Database, 2010ProductClaimEffectivenessSafetyAlli - OTCDecreasesEffective; weight-FDAversion ofabsorption ofloss amountsinvestigatingprescriptiondietary fattypically less forreports of liverdrug orlistatOTC versusinjury(Xenical)prescriptionBitter orangeIncreases caloriesInsufficientPossibly unsafeburnedreliable evidenceto rateChitosanBlocks absorptionInsufficientPossibly safeof dietary fatreliable evidenceto rateChromiumIncreases caloriesInsufficientLikely safeburned, decreasesreliable evidenceappetite andto ratebuilds muscleConjugatedReduces body fatPossibly effectivePossibly safelinoleic acidand builds muscle(CLA)CountryDecreasesInsufficientLikely unsafe andmallowappetite andreliable evidencebanned by FDA(heartleaf)increases caloriesto rateburnedEphedraDecreasesPossibly effectiveLikely unsafe andappetitebanned by FDAGreen teaIncreases calorieInsufficientPossibly safeextractand fatreliable evidencemetabolism andto ratedecreases appetiteGuar gumBlocks absorptionPossiblyLikely safeof dietary fat andineffectiveincreases feelingof fullnessHoodiaDecreasesInsufficientInsufficientappetitereliable evidenceinformationto rate
It is therefore an object of the present invention to provide safe, well characterized and efficacious compounds for effecting weight loss, and methods of use thereof.
It is a further object of the present invention to provide dosage forms, such as oral dosage forms, for the promotion of weight loss, and methods of use thereof.